I took a look at the package. It's not authored correctly. The .dlls have to be placed under a folder called 'lib' for them to be added as reference to the project. If it's your package, modify it and upload a new version. Otherwise, click on the link
﻿Contact Authors on this page to let the package authors know.
https://nuget.org/packages/ebay

No problem. In case you don't know yet, there's a program which allows you to examine the contents of any NuGet package easily. It's called NuGet Package Explorer (install it here
http://nuget.codeplex.com/releases/view/59864). That's how I checked the contents of your Ebay package.